How Long Does Postinor 2 Last In The Body?

Written ByPharm. John Published:
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The question “How long does Postinor 2 last in the body?” is a frequent question from both my female and male clients. 

Based on my experience as a Pharmacist, people who ask me this question often do so to know if it’d be safe to have unprotected intercourse again without having to take Postinor 2.

So basically, they just want to know if the contraceptive effect of the initial pill they took will last long enough to prevent pregnancy should they indulge in unprotected sex again a day or more after this first dose.

This article will provide all the answers you need. I will explain how long Postinor 2 lasts in the body, provide answers to another common question “How many days after taking Postinor 2 am I protected?”, and also discuss whether it will be safe to take another pill if you already took 1 for a first instance of unprotected intimacy. 

So keep reading.

Key points

  • Postinor 2 is effective in preventing pregnancy up to 72 hours after unprotected sex. It works best if taken within the first 24 hours.
  • On average, Postinor 2 stays in the body for at least 5 days (120 hours) before it is broken down and completely removed from the body through urine and feces. Its half-life is 24.4 hours, meaning the amount in the blood is reduced by half every 1 day.
  • Postinor 2 only prevents pregnancy from the unprotected sex that occurred before taking it. It does not continue working to prevent pregnancy from any subsequent unprotected sex after taking it.
  • Taking Postinor 2 repeatedly as a regular contraceptive rather than emergency contraception increases side effect risks. 

What Is Postinor 2?

green pack of postinor 2

Postinor 2 is a brand name for a synthetic (artificial) hormone called Levonorgestrel. 

It mimics the actions of progesterone which is a natural hormone produced in the ovaries in high amounts after ovulation (release of egg from the ovary).

Progesterone plays a huge role in pregnancy by making sure that a fertilized egg attaches properly to the wall of the uterus (womb). This allows the embryo to grow and develop successfully.

What levonorgestrel (Postinor 2) does is act like Progesterone but instead of promoting successful pregnancy, it acts to ensure that pregnancy doesn’t happen in the first place. 

It does so by blocking ovulation, making the wall of the uterus unsuitable for a fertilized egg to attach to (implant), and also by making the mucus in the cervix to thicken, thereby hindering the free movement of sperm towards the egg.

Postinor 2 is effective in preventing pregnancy if taken within the first 72 hours after unprotected sex. It is most effective if taken within the first 24 hours. 

It is available as 0.75 mg levonorgestrel and you can either take two tablets at once (i.e. 1.5 mg) or you take one tablet first and then the second tablet 12 hours after the first. 

All doses must be taken within the first 72 hours after unprotected intercourse in order for it to have a high chance of success.

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How Long Does Postinor 2 Last In The Body?

White pack of Postinor 2

Postinor 2 stays in the body for at least 5 days (120 hours) before it is completely broken down by the liver and then eliminated from the body in urine (20 – 67%) and in feces (21 – 34%). 

This length of time during which Postinor 2 remains in the body is estimated from its elimination half-life. 

Elimination half-life is the time it takes for the amount of drug (Postinor 2) in the bloodstream to reduce by half (50%). It gives a measure of how fast a drug is being removed from the body.

The average half-life of Levonorgestrel which is the active ingredient in Postinor 2 is 24.4 hours. 1 tablet of Postinor 2 contains 0.75 mg of levonorgestrel. So on average, it will take 24.4 hours (1 day) for the 0.75 mg of levonorgestrel in your blood to reduce by half (0.375 mg).

To estimate how long Postinor 2 will remain in your body before getting eliminated completely, you’ll have to follow an established general rule of thumb. 

This rule of thumb states that it takes approximately 5 half-lives for a drug to be considered effectively eliminated from the body. 

This means that after 5 half-lives, the amount of Postinor 2 in the bloodstream will be significantly reduced by 97%. At this concentration, the drug is considered to have reached a point where it has very little to no clinical impact on the body.

Since the half-life of Postinor 2 is 24.4 hours (1 day) and it takes 5 half-lives for a drug to be eliminated to an ineffective amount, it therefore means that it will take at least 5 days for Postinor 2 to be completely removed from the body.

You should keep in mind that the fact that Postinor 2 can last this long in the body does not mean that it will prevent pregnancy if you indulge in unprotected sex again during these 5 days. 

How Many Days After Taking Postinor 2 Am I Protected?

White pack of Postinor 2 with exposed satchet of pills

Postinor 2 only prevents pregnancy for the unprotected sex you had before taking the pill. Its effect does not extend for days to cover for the subsequent unprotected sex you may have later. 

This means that, if you have unprotected sex again after taking Postinor 2, the pill you took previously will not provide any protection against pregnancy in this new instance of unprotected sex.  

So, if you had unprotected intercourse let’s say yesterday and you took Postinor 2 immediately after it. If you have another one today, the Postinor 2 you took yesterday will not protect you from becoming pregnant as a result of the unprotected sex you had today.

To prevent pregnancy from this new instance, you will have to take the pill again which is not advisable. The reason is that Postinor 2 is meant to be taken only as an emergency contraception and not as a routine pill for long-term protection from pregnancy. 

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Taking it again will increase your risk of suffering side effects like headache, dizziness, breast tenderness, abdominal pain, nausea, vomiting, acne, menstrual irregularities, etc.

If you plan to indulge in more unprotected sex, it is advisable that you explore an alternative method of contraception such as the use of combined oral contraceptives (COCs).

COCs are available as tablets and are taken for 21 days. They are safer than using Postinor 2 regularly and also offer excellent protection against pregnancy.  They must be taken everyday and at the exact same time in order for it to be effective.

Final Thoughts

If you are asking how long Postinor 2 lasts in the body so as to decide if it will be necessary to take another dose for a new instance of unprotected, well the answer is 5 days.

However, the previous dose of the drug will not prevent you from getting from this new instance of unprotected intercourse. 

To prevent pregnancy again, you will have to retake it, and this is not advisable because it puts you at risk of experiencing side effects from the drug.

Instead, talk to your doctor about the possibility of being placed on another method of contraception as mentioned in the article. Always remember that Postinor 2 only prevents pregnancy but not infections.

References

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About the Pharmacist

Pharm. John

Pharm. John Mark (BPharm) is a licensed pharmacist with over 6 years of experience spanning clinical, community, and hospital pharmacy settings.

His wealth of experience and expertise makes him your knowledgeable and go-to source for all pharmacy and medication-related questions.

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